Abstract: When the Huayingshan tunnel intersected the Gaodingshan coal mine goaf, gas outbursts occurred. To address this issue, the sources, emission patterns, and potential risks of the gas are analyzed. A technical solution involving the use of advance curtain grouting rings for gas sealing is proposed, subsequently optimized, and its effectiveness tested and verified. The results demonstrate the following. (1) After the tunnel face intersects the goaf, gas from the goaf is injected into the tunnel owing to the pressure difference. Gas from the surrounding goaf and coal seam continuously recharges the goaf, leading to a sustained increase in gas concentration in the tunnel. (2) The curtain grouting process uses a full-hole one-time grouting method and a segmented forward grouting approach. Eight rounds of grouting holes are arranged at the tunnel face, forming a four-section trumpet-shaped curtain ring. These measures achieve an 80% curtain grouting filling rate, with the curtain ring effectively sealing cracks in the surrounding rock. (3) The detected gas concentration in the goaf hole decreases from 80% before grouting to 9.6% after grouting, demonstrating the effectiveness of this gas control technology for tunnels crossing coal mine goafs.

Key words: tunnel, gas control, gas sealing, advance curtain grouting, coal mine goaf